The radial run of the line optical depth is here parameterized as a power law: rho ~ r^(-n) (which might reflect a power law density structure of the supernova ejecta) . As n is decreased, the atmosphere extends out to higher velocities, and so the absorption and emission get wider. The emission peak also gets higher because there is more material to scatter light into the line of sight. However, the absorption minimum and the emission peak do not substantially move their wavelength position.